Can Roaches and Flies Transmit COVID?

Can the cockroaches and flies in your home transmit COVID-19 to you? It makes sense to worry since during the peak of the pandemic, the fear of dogs and cats transmitting the virus was very present.

Ever since the arrival of the virus in 2020, scientists and public health officials have worked arduously to figure out the nature of COVID and how it could be transmitted to humans. It is mostly contagious through airborne transmission, but it has also been shown to be found on surfaces where house pets can catch it.

What about common bugs, though? Are the flies that linger on the trash capable of carrying the virus? With cases like mosquitoes transmitting dengue, it makes sense to make the correlation. Fortunately, a recent study shows that SARS-CoV-2 does not replicate in insects.

This rules out the possibility of mechanical transmission with non-biting flies or other types of bugs. The study, held by a team of researchers from Texas A&M University, looked at cockroaches and flies in houses in Texas where the owners or pets had reported positive results of COVID. The results, published in late May in the Journal of Medical Entomology, showed that no bugs carried the virus or its RNA.

Associate professor of entomology at A&M Gabriel Hamer, Ph.D. led the study. Aside from testing if the bugs carried the virus, they also examined the potential of using cockroaches and house flies for xenosurveillance, which means the practice of sampling DNA from insects to monitor the presence of disease pathogens. This is helpful for collecting DNA or RNA from species that usually live in complex habitats or are small and elusive.

The study consisted of 133 sticky and liquid-baited insect traps spread across 40 homes in Bell, Montgomery, and Brazos counties in Texas. In the end, they were able to catch 1,345 insects belonging to 11 families of either flies or cockroaches. They also set 14 additional traps in the cases where a cat or dog had tested positive for COVID-19. None of the tests showed a single case of a bug carrying the virus.

This study and its results were a reversal of a previous study done by the team in a laboratory, showing SARS-CoV2 RNA on insects. “Given that we were sampling insects in homes with recent COVID-19 cases, some of which also had active animal shedding of SARS-CoV-2, we expected to find the nucleic acid from the virus on these insects,” Hamer explained for Entomology Today. “Instead, we did not detect evidence of the virus in the sample insects from these homes.”

These studies are crucial in helping humans understand how biological and mechanical transmission of a virus can occur, and what animals can transmit it to us. The pandemic may be much less critical than two years ago, but reality has shown us that we will have to live with COVID-19 for a long time, with cases spiking every now and then.